The present invention relates to a contact probe to which a large electric current can be supplied.
An example of a probe in the related art will be described referring to FIGS. 15 to 17. FIG. 15 is a vertical sectional view of the probe in the related art. FIG. 16 is a sectional view of a tube in FIG. 15 as seen in a direction of arrow marks A-A. FIG. 17 is a plan view showing a plurality of the probes as shown in FIG. 15 provided in a socket. In FIGS. 15 to 17, a probe 10 includes a tube 12 in a cylindrical shape having a relatively thin wall thickness and formed of electrically conductive metal, and plungers 14, 14 formed of electrically conductive metal which are contained in the tube 12 so as to be protruded and contracted in an axial direction so that their distal end parts may protrude outward but may not escape. Further, a coil spring 16 for elastically urging the plungers 14, 14 outward is contained in the tube 12 in a contracted state. A plurality of the probes 10 having the above described structure are arranged in a socket 18 formed of insulating material. In FIG. 17, a plurality of the probes 10 are arranged in the socket 18 at a determined pitch (for example, at a pitch of 0.5 mm) rectilinearly in two rows, as seen in a plan view. The probe 10 in the related art having the above described structure is disclosed in JP-A-2006-98254.
The distal end parts of the plungers 14, 14 at both ends of the probe 10 are respectively brought into elastic contact with a measuring terminal of a device to be measured and a terminal of a test jig, whereby the measuring terminal of the device to be measured is electrically connected to the terminal of the test jig. In this manner, there is formed an electrically connected circuit in which the measuring terminal of the device to be measured is successively connected, through one of the plungers 14, the tube 12, and the other plunger 14, to the terminal of the test jig, by bringing the plunger 14, 14 into elastic contact with an inner wall of the tube 12. Moreover, there is formed another electrically connected circuit in which the one plunger 14, the coil spring 16, and the other plunger 14 are successively connected.
In recent years, the measuring terminals of the device to be measured such as an electronic circuit are arranged at an extremely small pitch of 0.5 mm, for example. Then, the probes 10 are also arranged at a small pitch of 0.5 mm or so, and an outer diameter of the tube 12 is as small as 0.3 mm, in order to keep the adjacent tubes 12, 12 insulated from each other. For this reason, the tube 12 has a thin wall thickness and a small sectional area, and its conductor resistance is larger as compared with the plungers 14, 14 having a large sectional area. Therefore, in case where a large electric current is supplied to the probe 10, remarkable heat generation and a large drop of electric voltage occur in the tube 12. As the results, there has been such inconvenience that electric current of a desired large value can not be supplied. In the related art having the above described structure, the electric current which can be supplied to the probe 10 is 1 A at most.